Motor operated adjusting mechanism



Nov. 24, 1942. E. x. SCHMIDT 2,302,974 5 MOTOR OPERATED ADJUSTING MECHANISM Filed Aug. 4, 1940 s shuts-sheet 1 "435 23g; 3 J a :40: w

Z31 I 554-42 1416 /E, 59 54 A6 5 9 56 3 @A fi $255 Z5 J 51 m" 64 W9 0 5p 5 53 50 5a 5a 53 8% j 3? W Nov. 24, 1942.

E. x. SCHMIDT MOTOR OPERATED ADJUSTING MECHANISM Filed Au 4, 1940 s Sheets-Shet'Z Nov. 24, 1942;. w 5 x, SCHMmT 2,302,974

MOTOR OPERATED ADJUSTING MECHANISM I Filed Aug, 4, 1940 3 Sheets-Sheet 3 L 3 Moo 'novel means for insuring a Patented Nov. 24, 1942 MOTOR OPERATED ADJUSTING MECHANISM Edwin X. Schmidt, Milwaukee, Wis., assignor to Cutler-Hammer, poration of Delaware Inc., Milwaukee, Wis., a cor- Application August 4, 1940, Serial No. 351,313

13 Claims.

This invention relates to improvements in motor operated adjusting mechanisms.

A primary object of the invention is to provide temporarily accelerated rate of adjustment of an indicating and/or controlling device in one direction or the other upon each required change of adjustment thereof from one direction to the other, to thereby provide for more rapid and more accurate operation of such device.

Another object is to provide means for substantially reducing or minimizing the time period of the hunting cycle of the adjusting mechanism incident to each initial change in the direction of adjustment resulting from each opposite change in the value of a condition to be controlled.

Another object is to provide a motor operated adjusting mechanism of the aforementioned character whereby a control mechanism involving a minimum amount of operating force may be employed.

Another object is to provide an adjusting mechanism of the aforementioned character which is adapted to compensate to a inherent time lag in response of the control mechanism to changes in value of the condition to be controlled.

Another object is to provide an adjusting mechanism of the aforementioned character whereby the value of a condition tained substantially constant.

Another object is to provide a gas mixing control system wherein said adjusting mechanism may be employed.

Another object is to provide a gas mixing control system including two of said adjusting mechanisms, one of which is utilized to efiect proper proportioning of the combustible gases, and the other of which is adapted to efiect proper indication of the potential heating value of the gaseous mixture.

Another object is to provide a control system wherein said adjusting mechanism is utilized to provide for maintenance of a substantially constant temperature in a heating oven or the like.

Another object is to provide an adjusting mechanism including a novel form of gearing affording a negative lost motion between the driving and driven parts thereof.

Another object is to provide an adjusting mech anism including a slip clutch connection between the driving and driven elements, and means whereby said slip clutch connection is initially rendered fully effective for driving a part through large degree for the to be controlled is maina predetermined range at a relatively rapid rate and thereafter rendered efiective to drive said part at a relatively much slower rate.

Various other objects and advantages of the invention will hereinafter appear.

The accompanying drawings illustrate several embodiments and adaptations of my invention which will now be described-it being understood that the invention is susceptible of embodiment in other forms without departing from the scope of the appended claims.

In the drawings,

Figure 1 is a side elevational view (approximately one-half size) of a negative lost motion adjusting mechanism constructed in accordance with my invention, the same being adapted to control the rate of adjustment of a potentiometer or the like.

Fig. 2 is a topplan view of the device illustrated in Fig. 1.

Fig. 3 is an enlarged fragmentary sectional View, on the line 3-3 of Fig. 2, certain of the parts being shown in elevation.

Fig. 4 is an enlarged view of certain elements of the clutch mechanism.

Fig. 5 is a fragmentary view, in section on the line 5-5 of Fig. 3, showing the means for limiting the total range of driving or adjustment of the driven element in opposite directions respectively.

Fig. 6 is a fragmentary view, partly in section, showing a modification wherein my negative lost motion adjusting mechanism is adapted for adjustmentor control of a butterfly valve or the like.

Fig. 7 illustrates schematically and diagrammatically a gas mixing control system having my negative lost motion adjustment mechanisms applied both to the control of a potentiometer and to a valve for controlling the proportionality of one of the constituents of a gaseous mixture,

whereby the total heating value per unit volume of the latter is maintained substantially constant.

Fig. 8 is a schematic and diagrammatic illustration of a simplified form of gas mixing control system wherein my negative lost motion adjusting mechanism is associated with the proportioning valve.

Fig. 9 is a schematic and diagrammatic illustration of a system for the control of temperature in a heating oven or the like, wherein my negative lost motion adjusting mechanism is utilized to control the rate of supply of the combustible gaseous fuel.

Fig. 10 is a graphic illustration of a given trend in variation of the total heating value per unit volume of a gaseous fluid or a mixture of gaseous fluids, or in the value of potential heat units supplied per unit of time, which value it is desired to maintain substantially constant.

Fig. ll is a graphic illustration of the controlling eifect upon the heating value per unit volume of a combustible fluid, in the event of a variation such as that illustrated in Fig. 10, as provided by a known form of adjusting and controlling mechanism.

Fig. 12 graphically illustrates a condition like that involved in Figs. 10 and 11, as controlled by a system embodying my aforementioned negative lost motion adjusting mechanism, and

Fig. 13 is a graphic illustration similar to Fig. 12-but showing the effect of a reduction in the degree of lost motion provided between certain parts of my negative lost motion adjusting mechanism.

Referring first to Figs. 1 to 5, inclusive, the numeral iii (Figs. 2 and 3) designates a suitable relatively small, geared, reversible motor, which is adapted when in operation to drive a shaft It at a relatively slow speed; say, one revolution per minute. Motor 55 is preferably of the split-field reversible type, and any suitable means, such as those hereinafter described, may be employed to effect completion of the respective circuit connecticns thereof selectively, whereb the shaft it is rotated in one direction or the other or permitted to remain stationary. Shaft it is provided with a reduced end portion it (Fig. i) of circular form in transverse cross section which has a freely slidable or telescopic fit within a recess in the adjacent end of a shaft H, as shown in dotted lines at I'F in Fig. 4. Shaft H has keyed or otherwise non-rotatably attached to said end thereof a spur gear or pinion it, which as shown herein is provided with eight teeth.

A driving connection between shafts l5 and I? is provided by means of a pin l9 which preferably has a drive fit within an opening extending diametrically through the reduced portion it of shaft iii, the arrangement being such that substantially equal lengths of said pin extend from opposite sides of shaft portion I5 The end of gear i8 adjacent to shaft 65 is preferably provided with a diametrically extending groove w of approximately V-shape to normally accommodate the opposite ends of pin [9, as shown in Figs. 3 and 4, whereby shaft it may drive gear EB and, consequently, the shaft H. Shaft I! is so mounted and spring-biased in the manner hereinafter described, as to provide thereof in the manner illustrated in full lines in Fig. 4. However, upon positive restraint of rotation of shaft ll in one direction or the other, by the means hereinafter described, the ends of pin Hi are adapted to act upon one wall or the other of groove I8 to force endwise against said bias the gear i3, shaft I! and parts associated therewith, whereby shaft it may rotate independently of shaft ll.

As best illustrated in Figs. 2 and 3 motor i5 is for normal positioning panel or other suitable support. Said upper portion 27% of the bracket is provided with an opening 22 (Fig. 3) to accommodate the end bearing ii of the motor, from which shaft I 6 projects.

The lower portion of bracket 22 is provided with an opening 2? (Fig. 3) having a conical countersink 22 at its inner end. A shaft 23 (Fig. 3) has an integral flange or enlargement 23 of octagonal or other polygonal contour, the inner fiat face of which is adapted to abut against the outer face of said lower portion of bracket 22; said shaft having an inner end portion 23* which is adapted to fit snugly within opening 22 and said end portion 23 being upset or riveted against the peripheral wall of countersink 22 as shown t '23, to rigidly secure said shaft to said bracket. Shaft 23 has rotatably mounted thereon a relatively large gear 24, which meshes with gear l8, gear 24 preferably having one hundred and sixty teeth.

Thebearing hub of gear 26 is designated by the numeral 26*, said hub acting to space said gear from bracket 22 for normal full width engagement or meshing with pinion l8. Also rotatably supported upon shaft 23 is a gear 25, which preferably has one hundred and twenty-eight teeth, the bearing hub 25 of which acts to properly space the same from gear 24. Meshing with gear (normally at the left hand side of the teeth of the latter, Fig. 3) is a relatively narrower or thinner and smaller gear 25, which is preferably provided with forty teeth. Gear 26 is rotatably mounted upon the shaft [1, and the left-hand face or side thereof is frictionally engaged with a disk or plate 2'! which is non-rotatably attached to shaft 5?, as by means of a pin 28 which extends diametrically through the hub 27 of said disk and through shaft I! (see Figs. 3 and 4).

Pin 25 is preferably provided with an extension 28 of enlarged diameter which cooperates with one or the other of a pair of blocks or lugs 25 Zfi carried by a metal bracket 29 which is rigidly attached to gear 2 1, in the manner illustrated in Figs. 3 and 5, as by means of a plurality of screws 25, 253 and 21%. When extension 28 engages either of the blocks 23% or 29 the shaft I! is positively locked against further rotation in the direction in which it was being driven, with consequent stoppage of further rotation of gears 18, 2t, 24 and 25 in a corresponding direction.

Upon such locking of said gears pin is (which is carried by the continuously rotatable motor shaft it) acts to force shaft I1 endwise toward the right (Fig. 3) against its bias, thus permitting continued rotation of shaft l 6 independently of shaft H. During such endwise movement of shaft 57 pinion l3 and gear 26 are slid or displaced transversel relatively to the respective gears 2 and 25, without unmeshing said parts; thus insuring proper cooperation thereof upon reversal of the direction of rotation of motor l5.

As best illustrated in Fig. 3, a disk or plate 33 is rotatably mounted upon shaft l1, one fiat face of said plate being adapted for engagement with the adjacent face of gear 25. The means for biasing shaft i? toward the left (Fig. 3) and for holding plates 21 and Si) in frictional driving engagement with gear 25 preferably comprises a pair of coiled compression springs 3i and 32 which surround shaft ll. The right hand end of spring iii in Fig. 3 abuts against the connecting portion 35% of a substantially U-shaped bracket 33, the arms 33* and 33 of which have right angled perforated ends which are attached to the upper portion 2% of bracket 22 as by means of a pair of screws 34, 34 (Fig. 2). Portion 33 of bracket 33 is perforated to accommodate and provide a bearing and support for one end of shaft ll, as shown in Fig. 3.

The other end of spring 3| abuts against the projecting ends of a pin 35, which preferably has a drive fit within an opening provided in shaft I! at a predetermined point in its length. Spring 3| thus acts to bias shaft H and pinion |8 toward the left to the positions thereof shown in Fig. 3.

Spring 32 is interposed between pin 35 and the right hand face of plate (Fig. 3), thus biasing plate 30 against one face of gear 26. This arrangement affords a slip-clutch driving connection between shaft l1 and gear 26. Springs 3| and 32 are preferably provided with sheet metal cups at the respective ends thereof, as shown.

In Figs. 1 to 5 I have shown my invention applied to the control or adjustment of a potentiometer type resistance varying device, which is designated in general by the numeral 36, The movable contact means of said potentiometer preferably comprises a punched and stamped member 3'! composed of resilient sheet metal,

such as phosphor bronze. The flat body portion of member 3'! is rigidly attached to a flat insulating disk 38, as by means of two or more screws or rivets, one of which is shown at 39 in Fig. 3; disk 38 being in turn rigidly attached to gear 25, as by means of two or more screws 40.

Member 31 is provided with a pair of reflexed contact arms 3! and 31 the tips of which are preferably arranged in alinement with and on opposite sides of the shaft 24. The tip of arm '1' 31 is located rather closely adjacent to but spaced from shaft 23 for engagement with a predetermined degree of pressure against the stationary contact ring 36 carried by the insulating base 36 of the potentiometer; said contact ring 36 having a conducting plate 36 electrically connected thereto, and said plate having a wiring terminal portion 3K5 exposed at the periphery of base 36 The tip of arm 3! is spaced a substantially greater distance from shaft 23, whereby the same is adapted to engage at a variable point with the resistance wire coil 3%? (see Fig. 2) which is arranged in the form of an approximately complete circle and is carried by the insulating base The two ends of coil 36 are respectively electrically connected with a pair of wiring terminal members 36 and 36 the three terminals jointly providing for electrical connection of the potentiometer in circuit in the usual manner.

The manner in which base 36 is non-rotatably attached to shaft 23 is best illustrated in Fig. 3. Thus said base is provided with a centrally located through passage 36 which is adapted to freely accommodate a hollow ferrule 4| the exposed end portion of which is externally threaded, as shown at M to accommodate a clamping nut 42. The inner end of ferrule 4| is provided with a flange 4| which fits within a countersink or recess S in base 36, said nut acting to clamp the ferrule and base to each other. A metal washer 43 is preferably interposed between nut 42 and base 36.

Shaft 23 is provided with a portion 23 of reduced cross section onto which ferrule 4| is adapted to slidably fit, the outer end 23 of said shaft portion being threaded to accommodate a nut 44, whereby the ferrule 4| is clamped to shaft 23 as illustrated. A metal washer is preferably interposed between nut 44 and the outer end of ferrule 4|. The arrangement is such that upon assembly of the parts as aforedescribed the contact arms 3'! and 3'! will be bent or pressed toward plate 38 to a predetermined degree, thereby providing the desired degree of contact pressure of the respective tips thereof.

My device includes a stud or prong 46 which is rigidly attached to gear 25, as by means of a pair of screws 41, and projects radially therefrom to an extent sufiicient to provide for positive engagement thereof with one or the other of. the shank ends of a pair of screws or bolts 48 and 49, which are respectively adjustably carried by spaced lugs 29 and 2.! formed integrally with and upstanding from the base portion of bracket 29, which is attached to gear 24 as aforedescribed. As will be understood, screws 48 and 49 are adjustable (preferably to like degrees) as by means of a screwdriver, to provide for variation of the degree or range of lost motion between gears 25 and 24, for a purpose hereinafter described.

It will be apparent from the foregoing description that my device is properly referred to as a negative lost motion mechanism. That is to say, in an ordinary lost motion mechanism a change in the direction of movement or rotation of the driving element will result in a delay in picking up or engaging the driven element for driving of v the latter in the reverse direction; whereas with my arrangement upon a reversal of the direction of rotation of the driving element the driven element is not only immediately engaged for driving thereof in such reverse direction, but the rate of driving of the driven element is definitely increased or accelerated for a predetermined period of time. After the driven element is moved through a predetermined angle or distance at such accelerated rate, the lost motion between the elements of the gearing is taken up, whereupon the adjustable element (in this case the contactor member 31 of the potentiometer) is constrained to move at a predetermined relatively slow rate of speed. the slip-clutch connection between disks 21, 3|] and gear 26 being utilized to permit such slow speed adjustment of the driven element.

In the modified form of the device illustrated in Fig. 6 the gears 24 and 25 may be identical with the corresponding gears aforedescribed-it being understood that bracket 29 and its associated parts will be attached to gear 24 of Fig. 6 and that projection 46 will be attached to gear 25such elements being omitted from Fig. 6 merely for the purpose of better illustrating the actual changes required. Thus in Fig. 6 I employ a relatively short shaft 56 (instead of shaft 23 aforedescribed) upon which gears 24 and 25 are rotatably mounted, shaft 59 having portions 50*, 55 50, (corresponding with portions 23% 23 and 23 of shaft 23) to provide for rigid and non-rotatable attachment thereof to bracket 22. The reduced and threaded end 56 of said shaft is adapted to accommodate a nut Bil and washer 5|] to retain gears 24 and 25 in assembled relation to the Shaft while providing for relatively free rotation with respect thereto.

Gear 25 has rigidly and non rotatably attached thereto, as by means of a plurality of screws 5!, a member 5| which is formed to accommodate shaft end 56 and its associated parts 50 and 53, said member 5| having formed integrally therewith, and in concentric relation to shaft 50, a stub shaft 5| to which a hollow connecting ferrule 52 may be attached, as by means of a set screw 5%, said ferrule having associated therewith a second set screw 52* for clamping engagement with a shaft 53, whereby the latter will rotate in one direction or the other in unison with stub shaft El and gear 25. Shaft 53 may be directly attached to a valve, such as a butterfly valve, to provide for adjustment of the latter in the same manner as described in connection with the potentiometer aforementioned, such adjustment, as aioredescribed, having the negative lost motion characteristic, among others.

Referring now to Fig. 7, wherein I have shown my negative lost motion adjusting mechanism applied to a gas mixing control system to improve the operative characteristics of the latter, the numeral 54 designates a branch conduit through which a combustible gas of relatively high total heating value per unit Volume is adapted to flow in the direction indicated by the ar row, at a rate depending upon the adjustment of a butterfly valve or the like shown in dotted line at 55. Numeral 59 designates a second branch conduit through which a lean gas of a known constant total heatin value per unit vol ume, as, for instance, air, is adapted to flow at a constant volumetric rate per unit of time, from suitable source. Branch conduits 5% and 5%,; cc:.,.imunicate with a main conduit 5'? in which the aforementioned rich and lean gases are ed, and through which the resulting combus gaseous mixture is adapted to flow to disable or desired point of use or storage.

In practice it is desirable to maintain as near- 1y constant as possible the total heating value 1' unit volume of the combustible mixture flowg in conduit 5?. To this end, a continuous sample of the mixture is withdrawn from con-- duit supplied through piping 58 and E9 to a known form of calorimetric device, which is designated in general by the numeral Mean are also preferably provided to insure substantially atmospheric pressure of the sample supplied through piping as to device at, said means comprising an orifice plate or constricwhich preferably is in the form of a burner ill. The calorimetric device 65.) is preferably of the relatively quick-acting precision type described and claimed in my Patent No. 2,238,606, dated April 15, 1941, to which reference may be had for a detailed description of the construction and mode of operation thereof. Here the various elements forming part of or associated with the calorimetric devic it are designated by the same reference letters, or by the same reference numerals with a prime added, as in my aforementioned Patent No. 2,238,606.

More specifically S designates a resistor; S a slide wire resistor having an automatically adjustable contactor H; HJ the hot junction. elements; CJ the cold junction elements; iii the indicatin scale; G the galvanometer; RT a resistor subjected to the temperature of the tank liquid and responsive electrically to variations in said temperature; R a resistor having a fixed or constant resistance value; E3 a dry battery to supply current for the potentiometer circuit; hi adjustable resistance or rheostat for manually establishing the desired value of current flow .rom battery 93 to compensate for depletion or weakening of the latter; 29 a, milliammeter having connected in parallel therewith an adjustable resistance 2 i and milliammeter 2i! being utilized to assist in proper setting of the battery current by adjustment of rheostat I4; 25' designates 1011 $3 in pipe 5:3, and a vent to atmosphere in general the indicating and recording device associated with the calorimetric device 68, '12 being the indicator which cooperates 'ith scale it as well as the recorder for cooperation with the movable chart. The elements of Fig. '7, as thus far described are adapted to operate automatically, in the manner disclosed in my aforementioned Patent No. 2,233,608, to eiiect indication and recordatio-n of variations in the instantaneous total heating value per unit volume of the test gas.

However, in a gas mixing control system like that disclosed in Fig. '7 it is desired to effect automatic adjustment of the relative volumetric rates of flow of the rich and lean gases in such a manner as to compensate for variations in the total heating value per unit volume of the gaseous mixture. Accordingly the shaft (32 is rotatable in one direction or the other upon a departure of the needle of galvanometer G from its intermediate or null position, as an incident to an increase or a decrease in the total heating value per unit volume of the gaseous mixture. Shaft has fixed thereto, as by means or a set screw or the like, a radially extending contactcr 63,

which is movable in one direction from an intermediate or neutral position to engage a stationary contact 56, or in the opposite direction to engage a stationary contact 65. Contactor is preferably insulated from shaft 632 and has attached thereto a conductor 66 which leads to a stationary contact 67 forming part of a switch whose contactor 68 is normally biased to its closed position by spring means, as shown; said contactor being intermittently opened for a predetermined period as by means of a cam 69 which is continuously rotated by a motor it. As shown, cam 69 is preferably so formed as to provide for alternate opening and closing of contactc-r for substantially equal periods of time.

The system of Fig. '7 is preferably supplied with direct current from lines L L upon manual closure of a double-pole knife switch "i i, l i Thus if it be assumed that the total heating value per unit volume of the mixture flowing in conduit 57 increases beyond a value preselected therefor, the calorimetric device (it in response thereto will eilect operation of galvanometer G in a direction to cause, through the medium of the mechanism 25', rotation of shaft 62, say in a clockwise direction, with consequent engagement of contactor {33 with contact 64, Then, if contactor 5B is en gaged with contact (31!, or upon closure of said contactor, a circuit will be completed for motor 72 to efiect operation of the latter in a direction tending to effect movement of valve 55 toward its closed position.

If the valve 55 had last been moved toward its fully opened position, the operation of motor 12 just mentioned will act, through the negative 10st motion adjusting mechanism enclosed within casing 12' to eilect an initial relatively large degree, and relatively rapid rate of adjustment of valve 55 toward its closed position. If such adjustment of valve 55 is suiiicient to reduce the total heating value per unit volume of the mixture in conduit 5'! below the desired value thereof, the calorimetric device 63 will respond in such manner as to eiiect unbalancing of galvanometer G in an opposite sense or direction, with consequent rotation of shaft 62 in a clockwise direction to eifect disengagement of contactor 63 from contact 6 On the other hand, if such adjustment of valve 55 toward closed position is not suficient to reduce the total heating value per unit volume of the mixture below that preselected therefor, the contactor 63 will remain in engagement with contact 64, so that upon the next period of engagement of contactor 68 with contact 61 the motor 12 will again be energized for operation thereof in a direction tending to effect further movement of valve 55 toward closed position. Under these conditions, however, the lost motion between the gears of the negative lost motion adjusting mechanism will have been taken up, so that farther adjustment of valve 55 toward closed position will be effected at a much slower rate than that. initially provided therefor. The time period during which contactor 58 is disengaged from contact 61, by reason of the shape or form of cam 69, is preferably of such length as to permit the calorimetric device 50 to respond to a given adjustment of valve 55 before effecting another adjustment of the latter.

Similarly, if it be assumed that the total heating value per unit volume of the mixture in conduit 57 drops below that preselected therefor, the device 50 will respond to effect unbalancing of galvanometer G in an opposite direction from that aforedescribed. As a consequence shaft 62 will be moved in a counterclockwise direction until contactor 63 is engaged with contact 65, whereupon, during the period of intermittent engagement of contactor 68 with contact 67, a circuit will be completed for motor 72 for effecting operation thereof in a direction tending to effect opening movement of valve 55. Due to the provision of my negative lost motion mechanism, as aforedescribed, the initial adjustment of valve 55 toward its fully open position will be effected at a relatively rapid rate and to a relatively large degree, pending take-up of the aforementioned lost motion between gears 25 and 24. Subsequent adjustments of valve 55 toward open position, if necessary, will be made at a relatively slower rate, as controlled by the rate of movement of the large gear 24.

As will be apparent to those skilled in the art, the negative lost motion mechanism associated with valve 55 provides for a relatively more rapid rate of adjustment thereof temporarily following a change in the direction of adjustment of the control means, than would be possible with calorimetric devices of the prior art. The principal advantage of my control system embodying the negative lost motion mechanism, over a system lacking such mechanism, resides in the shortening of the hunting cycle. For example, in a given installation and under given conditions of variation in the total heating value per unit volume of the mixture the hunting cycle was found to be thirteen minutes; whereas in the same installation and under like conditions of variation, but with the negative lost motion mechanism omitted, the hunting cycle was found to be approximately twenty-three minutes. Although in the two instances just mentioned the heating value variations were approximately the same, the shorter hunting cycle resulting from the use of my negative lost motion mechanism represents a much closer control of the total heating value per unit volume of the mixture, with consequent insured maintenance of more nearly the desired total heating value per unit volume.

Although the calorimetric device 69 is of the relatively quick-acting precision type disclosed in my aforementioned Patent No. 2,238,606, it is desirable in certain installations to provide for even closer accuracy and continuous automatic depending upon whether the total heating value per unit volume of the mixture in conduit 51, as determined by device 13, goes above or below the value preselected therefor. As shown, contactor 75 is connected by conductor 78 with a stationary contact 19, into and out of engagement with which a contactor 80 is moved intermittently through the medium of a cam 8 l, which is preferably like and driven simultaneously with the cam 69 aforedescribed through the medium of the single motor 70 aforementioned. Calorimeter I3 is supplied with a sample of the mixture from conduit 57 through the medium of the aforementioned pipe 58 and a branch pipe 82, the orifice 53 and burner 6| likewise insuring substantially atmospheric pressure of the sample supplied to calorimeter 73.

An adjustable potentiometric type resistance varying device 83 has its contactor 85 connected with one terminal of galvanometer G, wherefore any change in the angular position of contactor 84 effects a corresponding change or correction in the calibration of the calorimetric device 60. The means for effecting adjustment of contactor 84' comprises a split-field reversible motor 85, like the motor 12 aforedescribed. Moreover, the driving connection between motor 85 and the shaft 85 which carries contactor 84 includes my aforementioned lost motion mechanism, which is enclosed within a housing 81 (like the housing 12' associated with motor 72).

checking of the device 50, as by means of a rela- Thus, assuming a predetermined rise in the total heating value per unit volume of the gaseous mixture above the value preselected therefor, as determined by the calorimeter 73, contactor 15 will engage contact It to effect energization and operation of motor 85 in a direction to effect such adjustment of contactor 84 as will result in proper and precision calibration of the control circuits (as, for instance, of the operating coil of galvanometer G) of calorimeter 50. More particularly, the aforementioned negative lost motion mechanism will cause an initial relatively rapid rate and relatively large degree of adjustment of contactor 84, during the period of engagement of contactor with contact 79, and pending take-up of the aforementioned lost motion between gear 25 and gear 24 (see Figs. 1 to 5). If contactor 15 remains in engagement with contact 18 upon the next period of engagement of contactor 30 with contact '19, a further adjustment of contactor 84 in the same direction, but at a much-slower rate (and consequently of much smaller degree during the period of engagement of contactor 80 with contact 79) will be effected. Upon a predetermined fall in the total heating value of the gaseous mixture (either initially or as an incident of the hunting cycle) contactor 15 will be engaged with contact 11, so that during the first period of engagement of contactor 80 with contact 19 thereafter the motor 85 will be operated in the reverse direction from that aforedescribed, and the negative lost motion mechanism will act to effect a relatively rapid and relatively large degree of movement of contactor 8 1 in a corresponding direction. The adjustment of contactor (i l in reverse directions is repeated until no further adjustment thereof is necessary, whereupon the indicating and recording device 14 attains equilibrium, with consequent neutral positioning of its contactor l5, thus indicating that the calorimeter 63 has been properly calibrated automatically, and that the desired total heating value per unit volume of the gaseous mixture in conduit 57 has been attained.

In the simplified form of gas mixing control apparatus illustrated more or less diagrammatically in Fig. 8, all of the parts may be identical with corresponding parts in Fig. '7, which parts have been given like numerals of reference. Thus the rich gas is supplied through a branch conduit 54 having therein a butterfly valve 55 for controlling the volumetric rate of flow of gas therethrough. Air or other lean gas of predetermined constant total heating value per unit volume is.

supplied at a constant volumetric rate through branch conduit 55, said branch conduits opening to main conduit 57 wherein said gases are mixed and thence conveyed to a point of use or storage. A continuous sample of the gaseous mixture is withdrawn from conduit 51 through piping 5S and 59 (constriction 55 and burner 6| providing for substantially atmospheric pressure of such sample) and supplied to the calorimetric device 55, which as aforedescribed is preferably of the quick-acting precision type disclosed in my aforementioned Patent No. 2,238,606. However, as will be understood by those skilled in the art, a relatively slower acting precision type calorimeter like that disclosed at 13 in Fig. 7 might be substituted for the calorimeter 50, if desired.

As shown, calorimeter 60 is provided with a contactor 53 which is movable automatically in one direction or the other from an intermediate or neutral position thereof into engagement with" one or the other of the contacts 64 or 85, depending upon whether the total heating value per unit volume of the mixture rises or falls with respect to the value preselected therefor. Thus upon a predetermined rise in the total heating value per unit volume of the mixture it may be assumed that contactor 53 will engage contact at, with consequent energization and operation of the split-field motor 12 in a manner tending to effect movement of valve 55 toward fully closed position. Due to the presence of my negative lost motion mechanism 12' as aforedescribed a relatively large degree and a relatively rapid rate of movement of valve 55 toward closed position is effected, pending the taking up of the lost motion between gears 25 and 24 (Figs. 1 to 6). Thereafter the closing movement of valve 55 is continued (but at a relatively much slower rate) pending attainment of the desired total heating value per unit volume of the mixture with resultant balancing of the galvanometer circuit and consequent movement of contactor 53 to an intermediate or neutral position.

If desired, of course, an interrupter (like parts 61, 68, 69 and 19 of Fig. '7) may be provided in the conductor 65, to permit the effect of a given adjustment of valve 55 to be determined by calorimeter 69 prior to effecting a further adjustment of the valve.

The operation of the device of Fig. 8 in the event of a drop in the total heating value per unit volume of the mixture below the value preselected therefor (either as a result of the aforementioned closing movement of valve 55 or as a result of a decrease in the total heating value of the gas in branch conduit 54) is believed to be apparent. Thus, under the conditions just mentioned the contactor E3 will be caused to engage contact 55, thereby effecting energization of motor 12 to cause operation thereof in the reverse direction. Such reverse operation of motor 12 will effect adjustment of valve 55 toward its fully open position, and due to the provision of said negative lost motion mechanism, said valve will be opened to a relatively large degree and at a relatively rapid rate, until the lost motion is again taken up between gear 25 and gear 24; whereupon further opening movement of the valve 55 will be effected at a relatively much slower rate, as determined by the rate of movement of gear 24.

In Fig. 9 I have shown my negative lost motion adjusting mechanism applied to the control of a butterfly valve or the like adapted to regulate the volumetric rate of supply of a combustible fluid to a heating oven or the like whereby the temperature Within the latter is maintained substantially constant. Thus the numeral 88 designates a conduit through which a combustible gaseous fluid is adapted to flow under pressure from any suitable source. In practice the fluid flowing in conduit 88 will be subject to relatively wide variations in total heating value per unit volume thereof, wherefore variation in the volumetric rate of flow thereof to the burner 89 in oven 90 is necessary to provide for maintenance of a predetermined substantially constant temperature in the latter, assuming that a substantially constant number of heat units per unit of time are absorbed by the articles (not shown) to be treated in oven 90 or are dissipated from the oven by diffusion or otherwise.

On the other hand, even though the total heating value per unit volume of the fluid flowing in conduit 88 remains substantially constant, regulation of the rate of flow thereof by adjustment of valve 55 may be necessary due to variations in the rate of heat absorption from oven 90 (as by variation in the number of articles treated therein per unit of time, or by variation in the rate of heat dissipation from the oven by variations in ambient or external temperature, and variations in the frequency with which the oven is charged with articles to be heat treated). My system of oven temperature control functions equally well under all of the conditions aforementioned, or combinations of such conditions.

As will be noted, conduit 88 has its forward end 88 reduced in diameter for positioning thereof within and in spaced relation to the surrounding wall of the enlarged tubular inlet end 89 of burner 89. The combustible gas ejected from the reduced end or nozzle 88 of conduit 88 thus acts as an injector to draw into the inlet end 89 a proper volume of air for mixture with the combustible gas, which mixture is ignited and burned within oven 90, as indicated by the multiple jets or flames 9 I.

The temperature within oven 90 is preferably ascertained by one or more thermocouples, the thermocouple 92 illustrated acting in the usual or well known manner to effect generation of an electromotive force or electric current whose value is proportional to or corresponds with the value of the temperature within oven 90. Such electromotive force is utilized to control the operation of the contactor 93 of a so-called polarized relay 93, whose operating coil 93 is electrically connected in a well known manner with the terminals of the thermocouple 92. As shown diagrammatically contactor 93 is preferably biased, as by a spring 93 or otherwise to one of its extreme positions wherein it engages the stationary contact 93 of the relay.

It may be assumed that contactor 93* en ages contact 93 when the temperature within oven 90 is below the value preselected therefor, and under these conditions a circuit will be com pleted intermittently, said circuit extending from line L by conductor 94 through the contacts 95 of a switch (when closed intermittently through the medium of a cam 96 which is adapted for continuous rotation by a suitable motor 91), thence by conductor 98 through contactor 913 and contact 93 conductor 99 through the closing winding I of an electromagnetically operable switch, whose normally open contacts are shown at 100*, and thence by conductors llll, I62 and I03 to line L Contacts tim when thus closed intermittently for a period depending upon the period of closure of contacts 95, are adapted to complete a circuit for the split field motor 12 for operation of the latter in one direction, which direction may be assumed to be such as to tend to effect opening movement of valve 55.

Due to the provision of my lost motion adjusting mechanism l2 (shown in detail in Figs. 1 to 6) a relatively rapid rate of opening movement of valve 55 is efiected during initial closure of contacts es, and during subsequent closure of said contacts, until the aforedescribed lost motion between gear 25 and the gear 24 is taken up. If the contactor thi remains in engagement with contact 93 the subsequent opening adjustments of valve 55 will be eiiected at a much slower rate (as determined by the rate of rotation of gear.

24) When the desired temperature is eventually attained or exceeded within oven 90 contactor 93 will be first disengaged from contact 93 to discontinue operation of motor 72 in a direction to eiiect further opening of valve 55, and if the temperature within oven Eli! exceeds the preselected value, contactor 93* will be moved in an obvious manner into engagement with contact 83 Thereupon (during intermittent closure of contacts 9%) a circuit will be completed in an obvious manner for the operating winding Hi l of a second electromagnetically operable switch, the normally open contacts of which are shown at lM Contacts lil t 'when closed intermittently are adapted to complete a reverse circuit for motor 72, whereby the latter tends to drive valve 55 toward its fully closed position. Upon such reversal of motor l2 said negative lost motion mechanism l2 acts to initially eiiect a relatively rapid rate and relatively large degree of closing movement of valve 55, during closure of contacts 95, and until the lost motion between gear 25 and gear 2 1 is taken up. Further closing movement of valve 55, if necessary, will be effected at a relatively much slower rate, as determined by the speed or rate of rotation of gear 2t, Upon reduction of the temperature within oven 98 or below the value preselected therefor contactor 93 will be permitted to disengage contact 93, and further adjustment of valve 55 will be discontinued pending re-engagement of said contactor with either of the aforementioned con- I, tacts 93 or 93 as will be readily understood.

In Fig. 10 the curve at A illustrates the actual total heating value per unit volume of a combustible gaseous mixture, which value maybe assumed to be that desired or preselected for a given purpose, as indicated by the horizontal line B. The downwardly angled portion A of curve A indicates the manner in which a given change in the total heating value per unit volume of the combustible mixture may take effect (assuming that there is no adjustment made in the volumetric proportionality of. the rich and lean gaseous constituents of the mixture, and hence no control of the total heating value per unit volume of the mixture), the resultant new actual total heating value being eventually stabilized as indicated at A which value is substantially lower than the desired or preselected value B. The dotted line C shows the manner in which the change in heating value would be indicated by a calorimetric device, the distance between the portion A of curve A and line C indicating the time lag in response of such calorimetric device.

Fig. 11 graphically illustrates the manner in which the condition illustrated in Fig. 10 would be handled by the various systems illustrated herein, if my negative lost motion adjusting mechanism were omitted therefrom. Thus the short horizontal line B may be considered to indicate coincidence of the actual and desired or preselected total heating value per unit volume of a combustible mixture, which corresponds with the aforementioned value A (and B) in Fig. 10. The portion D of the solid curved line indicates the actual change (decrease) in total heating value of the mixture. The substantially parallel downwardly angled line E formed of dashes to the right of portion D shows the actual indication 'of the total heating value by the calorimetric device, the spacing of said lines indicating the time lag of the calorimeter in responding to the change in heating value.

The point F illustrates diagrammatically the time at which the calorimeter responds to the change and attempts to adjust the valve or the like to increase the total heating value of the mixture. However, due to lost motion in the gearing, etc., no adjustment in the heating value is effected at points F, G and H, but when the point I in time is reached the lost motion will have been taken up, and a relatively slow and correspondingly small adjustment (opening) of the valve will be effected, to increase the actual heating value to that shown at J. Thereafter during corresponding time periods like small adjustments of the valve will be effected to increase the heating value of the mixture, as indicated at K, L and M.

During the next time period the valve will be further opened to increase the actual heating value of the mixture to that indicated at N, which, of course, is slightly above the value B preselected therefor. At such time period however, as indicated in dotted lines at Q, the heating value indicated by the calorimeter is substantially below the value B as an incident to the time lag in response of the calorimeter. Accordingly the valve is further opened to provide the actual heating values indicated at O and P. Prior to the next period for adjustment of the valve the indicated heating value will be at the point marked R in dotted lines and the. calorimetric device will act to prevent any further opening adjustment of the valve.

The heating value indicated by the calorimeter will continue to rise until the point S is reached,

- whereupon the calorimeter will respond and attempt to effect a closing adjustment of the valve, as indicated at T; but due to the aforementioned lost motion in the gearing, etc., no adjustment will be effected at any of the points T, U or V. When the point W, in time, is reached said lost motion will have been taken up and a closing adjustment of the valve will be effected, to reduce the total heating value of the mixture to that shown at X. Further closing adjustments are efiected', as indicated by the values X X X and X whereas when the value X is reached, and before the next adjustment period has arrived, the indicated total heating value will be as shown at point Y, so that the elements of the calorimeter will act to prevent further closing adjustment of the valve.

The actual total heating value X will be maintained until the point Z is reached, whereupon the calorimeter will attempt to effect opening adjustments of the valve at each of the points Z Z and Z but no adjustment can be made (due to the lost motion in the gearing) until point Z is reached, whereupon the total heating value will be increased in sequence to the values Z Z and Z", the latter value being only slightly above the preselected value. As will be noted the degree of divergence of the actual total heating value from the preselected value becomes smaller and smaller after each series of opening and/or closing adjustments of the valve, until stabilization of the actual heat ing value at the preselected value is eventually eiTec-ted. In like manner the variations indicated by the calorimeter are gradually decreased in magnitude, as shown by the dash-line curve E, etc.

The improvement in the control functions of the gas mixing control system or the like when my negative lost motion mechanism is employed is graphically illustrated in Fig. 12; wherein the portions B D and E of the curves may be considered to indicate the same values as in Fig. 11. On the other hand when point F is reached (Fig, 12) the calorimeter is immediately effective to cause an opening adjustment of the valve;

and, assuming a relatively large degree of separation of the abutment ends of the shanks of screws 48 and 49 (Fig. 1) to provide a relatively large degree of lost motion between gear and gear 24, a correspondingly large degree of opening adjustment of the valve will be efiected (as indicated at F in Fig. 12) so that the actual heating value F will be attained. Thereafter a series of relatively small opening adjustments of the valve will be effected (corresponding to those illustrated in Fig. 11) to sequentially provide for attainment of the heating values F F F F and F Due to the magnitude of the adjustment F the calorimeter will earlier respond to the initial increase in heating value of the mixture, and also due to the earlier effective response of the calorimeter for making the initial adjustment, the lengths of the waves of the actual and indicated variations in the total heating value of the mixture will be much smaller than those illustrated in Fig. 11. Also due to said earlier effective response of the calorimeter initially, the magnitudes of the variations in the actual and indicated values of said total heating value will likewise be reduced by employment of my negative lost motion adjusting mechanism. The further graphic illustration in Fig. 12 of the operations and functions of the control mechanism with my improvement incorporated therein are believed to be self-evident. As heretofore pointed out, I provide for a substantial reduction in the length of the hunting or stabilizing cycle, with a consequent closer and more accurate control of the total heating value of the mixture.

Fig. 13 graphically illustrates the manner in which the control system, including my negative lost motion adjusting mechanism responds to conditions like those illustrated in Fig. 12. In respect of 13, however, it is to be understood that the abutment ends of screws 48 and 49 (Fig. 1) will be adjusted or positioned relatively closely to each other to provide only a relatively small degree of lost motion between gear 25 and gear 24. Thus although the calorimeter will be effective immediately at point F (Fig. 13, the same as in Fig. 12) to cause an opening adjustment of the valve, nevertheless the degree of opening adjustment will be relatively small, as indicated by the line F showing the change in actual total heating value of the mixture. The following series of opening adjustments of the valve will be substantially equal to the initial adjustment, until the actual total heating value F is attained. Thereafter the control mechanism will function in the manner graphically illustrated in Fig. 13 to alternately effect series of closing and opening adjustments of the valve pending final attainment or stabilization of the total heating value of the mixture at the value preselected therefor. Although Figs. 12 and 13 respectively represent the effect of adjusting the screws 43 and 49 (Fig. 1) to provide substantially maximum and substantially minimum degrees of lost motion between gears 25 and 24, it is to be understood that various other degrees of adjustment of either or both of the screws 48 and 49 may be effected, as may be desired to meet the particular characteristics of the calorimetric device (in respect of time lag in response,

etc.), or other conditions of a particular installation.

What I claim as new and desire to secure by Letters Patent is:

1. In a gas mixing control system, in combination, a pair of branch conduits through which a rich gas of variable total heating value per unit volume and a lean gas of constant total heating value per unit volume are respectively adapted to flow, a main conduit into which said branch conduits discharge to provide for mixture of said gases, an adjustable valve in one of said branch conduits, means for automatically adjusting said valve to vary the volumetric proportionality of said gases whereby the total heating value per unit volume of the mixture is maintained substantially constant, said last mentioned means comprising a calorimetric device adapted to continuously burn a volumetrically constant sample of said mixture to ascertain the total heating value per unit volume thereof, a reversible electric motor subject to control by said calorimetric device, gearing interposed between said motor and said valve to provide for opening or closing movement of the latter in accordance with the direction of operation of said motor, and means associated with said gearing to compensate for inherent lost motion in the latter as an incident to each reversal of the direction of rotation of said motor, said last mentioned means providing for initial opening or closing movement of said valve at a rate faster than normal upon each reversal of the direction of rotation of said motor.

2. In a gas mixing control system, in comasoaom bination, a pair of branch conduits through which a rich gas of variable total heating value per unit volume and a lean gas of constant total heating value per unit volume are respectively adapted to flow, a main conduit into which said branch conduits discharge to provide for mixture of said gases, an adjustable valve in one of said branch conduits, means for automatically adjusting said valve to vary the volumetric proportionality of said gases whereby the total heating value per unit volume of the mixture is maintained substantially constant, said last mentioned means comprising a calorimetric device adapted to continuously burn a volumetrically constant sample of said mixture to ascertain the total heating value per unit volume thereof, a reversible electric motor subject to control by said calorimetric device, gearing interposed between said motor and said valve to provide for opening or closing movement of the latter in accordance with the direction of operation of said motor, and means associated with said gearing to compensate for inherent lost motion in the latter as an incident to each reversal of the direction of rotation of said motor, said last mentioned means including a slip clutch driving connection between said motor and certain of the gears of said gearing, to thereby provide for initial opening or closing movement of said valve at a rate faster than normal upon each reversal of the direction of rotation of said motor.

3. In a gas mixing control system, in combination, a pair of branch conduits through which a rich gas of variable total heating value per unit volume and a lean gas of constant total heating value per unit volume are respectively adapted to ilow, a main conduit into which said branch conduits discharge toprovide for mixture of said gases, an adjustable valve in one of said branch conduits, means for automatically adjusting said valve to vary the volumetric proportionality of said gases whereby the total heating value per unit volume of the mixture is maintained substantially constant, said last mentioned means comprising a calorimetric device adapted to continuously burn a volumetrically constant sample of said mixture to ascertain the total heating value per unit volume thereof, a reversible electric motor subject to control by said calorimetric device, gearing interposed between said motor and said valve to provide for opening or closing movement of the latter in accordance with the direction of operation of said motor, means associated with said gearing to compensate forinherent lost motion in the latter as an incident to each reversal of the direction of rotation of said motor, a said last mentioned means including 'a slip clutch driving connection between said motor and certain of the gears of said gearing, and said last mentioned means also including a manually adjustable lost motion driving connection between certain of the gears of said gearing, to thereby provide for initial opening or closing movement of said valve at a rate faster than normal upon each reversal of the direction of rotation of said motor.

4. In a gas mixing control system, in combination, a pair of branch conduits through which a rich gas of variable total heating value per unit volume and a lean gas of constant total heating value per unit volume are respectively adapted to flow, a main conduit into which said branch conduits discharge to provide for mixture of said gases, an adjustable valve in one of said branch valve to vary the volumetric proportionality of said gases whereby the total heating "value per unit volume of the mixture is maintained substantially constant, said last mentioned means comprising a calorimetric device adapted to continuously burn a volumetrically constant sample of said mixture toascertain the total heating value per unit volume thereof, a reversible electric motor subject to control by said calorimetric device, gearing interposed between said motor and said valve to provide for opening or closing movement of the latter in accordance with the direction of operation of said motor, means associated with said gearing to compensate for inherent lost motion in the latter as an incident to each reversal of, the direction of rotation of said motor, said last mentioned means including a slip clutch driving connection a between said motor and certain of the gears of said gearing, said last mentioned means also including a manually adjustable lost motion driving connection between certain of the gears of said gearing, and said lost motion driving connection between said last mentioned gears providing for initial opening or closingmovement of said valve at a rate faster than normal upon each reversal of the direction of rotation of said motor.

5. In a gas mixing control system, in combination, a pair of .branch conduits through which a rich gas of variable total heatingvalue per unit volume and a leangas of constant total conduits, means for automatically adjusting said portionality of said gases whereby the total heat- 7 ing value per unit volume of the mixture is maintained substantially constant, said last mentioned means comprising a calorimetric device adapted to continuously burn a volumetrically constant sample of said mixture to ascertain the total heating value per unit volume thereof, a reversible electric motor subject to control by said calorimetric device, gearing interposed between said motor and said valve to provide for opening or closing movement of the latter in accordance with the direction of operation of said motor, means associated with said gearing to compensate for inherent lost motion in the latter as an incident to each reversal of the direction of rotation of said motor, said last mentioned means including a slip clutch driving connection between said motor and certain of the gears of said gearing, said last mentioned means also including a manually adjustable lost motion driving connection between certain of the gears of said gearing, said lost motion driving connection between said last mentioned gears providing for initial opening'or closing movement of said valve at a rate faster than normal upon each reversal of the direction of rotation of said motor, said calorimetric device being of the relatively quickacting precision type, a relatively slower acting precision type calorimetric device also adapted to continuously burn a volumetrically constant sample of said mixture to ascertain the total heating value per unit volume of the'latter, a second reversible electric motor subject to control by said last mentioned calorimetric device for operation of the former in one direction or the other in response to an increase or decrease in the indicated total heating value per unit volume of said mixture with respect to a value preselected therefor, a potentiometer type rheostat included in circuit with said calorimetric device first mentioned to provide for calibration of the latter, and means including gearing providing a negative lost motion driving connection between said second motor and a movable element of said potentiometer rheostat, said negative lost motion driving connection initially providing for substantially instantaneous operation of said movable element upon each reversal of operation of said second motor, to thereby compensate for the inherent lost motion in said gearing.

6. In a gas mixing control system, in combination, a pair of branch conduits through which a rich gas of variable total heating value per unit volume and a lean gas of constant total heating value per unit volume are respectively adapted to flow, a main conduit into which said branch conduits discharge to provide for mixture of said gases, an adjustable valve in one of said branch conduits, means for automatically adjusting said valve to vary the volumetric proportionality of said gases whereby the total heating value per unit Volume of the mixture is maintained substantially constant, said last mentioned means comprising a calorimetric device adapted to continuously burn a volumetrically constant sample of said mixture to ascertain the total heating value per unit volume thereof, a reversible electric motor subject to control by said calorimetric device, gearing interposed between said motor and said valve to provide for opening or closing movement of the latter in accordance with the direction of operation of said motor, means associated with said gearing to compensate for inherent lost motion in the-latter as an incident to each reversal of the direction of rotation of said motor, said last mentioned means including a slip clutch driving connection between said motor and certain of the gears of said gearing, said last mentioned means also including a manually adjustable lost motion driving connection between certain of the gears of said gearing, said lost motion driving connection between said last mentioned gears providing for initial opening or closing movement of said valve at a rate faster than normal upon each reversal of the direction of rotation of said motor, said calorimetric device being of the relatively quick-acting precision type, a relatively slower acting precision type calorimetric device also adapted to continuously burn a volumetrically constant sample of said mixture to ascertain the total heating value per unit volume of the latter, a second reversible electric motor subject to control by said last mentioned calorimetric device for operation of the former in one direction or the other in response to an increase or decrease in the indicated total heating value per unit volume of said mixture with respect to a value preselected therefor, a potentiometer type rheostat included in circuit with said calorimetric device first mentioned to provide for calibration of the latter, and means including gearing and a slip clutch providing a negative lost motion driving connection between said second motor and a movable element of said potentiometer rheostat, certain of the gears of said gearing having an adjustable lost motion connection therebetween whereby said slip clutch is rendered effective to cause a relatively rapid and relatively large initial adjustment of said movable element upon each reversal of operation of said second motor pending take-up of the lost motion between said gear, and said gears being 7 5 adapted to thereafter reduce the rate of adjustment of said element.

7. In a gas mixing control system, in combination, a pair of branch conduits through which a rich gas of variable total heating value per unit volume and a lean gas of constant total heating value per unit volume are respectively adapted to flow, a main conduit into which said branch conduits discharge to provide for mixture of said gases, an adjustable valve in one of said branch conduits, means for automatically adjusting said valve to vary the Volumetric proportionality of said gases whereby the total heating value per unit volume of the mixture is maintained substantially constant, said last mentioned means comprising a calorimetric device adapted to continuously burn a volumetrically constant sample of said mixture to ascertain the total heating value per unit volume thereof, a reversible electric motor subject to control by said calorimetric device, gearing interposed between said motor and said valve to provide for opening or closing movement of the latter in accordance with the direction of operation of said motor, means associated with said gearing to compensate for inherent lost motion in the latter as an incident to each reversal of the direction of rotation of said motor, said last mentioned means including a slip clutch driving connection between said motor and certain of the gears of said gearing, said last mentioned means also including a manually adjustable lost motion driving connection betwen certain of the gears of said gearing, said lost motion driving connection between said last mentioned gears providing for initial opening or closing movement of said valve at a rate faster than normal upon each reversal of the direction of rotation of said motor, said calorimetric device being of the relatively quickacting precision type, a relatively slower acting precision type calorimetric device also adapted to continuously burn a volumetrically constant sample of said mixture to ascertain the total heating value per unit volume of the latter, a second reversible electric motor subject to control by said last mentioned calorimetric device for operation of the former in one direction or the other in response to an increase or decrease in the indicated total heating value per unit volume of said mixture with respect to a value preselected therefor, a potentiometer type rheostat included in circuit with said calorimetric device first mentioned to provide for calibration of the latter, and means including gearing and a slip clutch providing a negative lost motion driving connection between said second motor and a movable element of said potentiometer rheostat, certain of the gears of said gearing having an adjustable lost motion connection therebetween whereby said slip clutch is rendered efiective to cause a relatively rapid and relatively large initial adjustment of said movable element upon each reversal of operation of said second motor pending take-up of the lost motion between said gears, said gears being adapted to thereafter reduce the rate of adjustment of said element, and associated means adapted to intermittently interrupt operation of either or both of said motors under all conditions tending to effect operation thereof, for the purpose set forth- 8. In a control system, in combination, means responsive to variations in a condition such as temperature, means subject to control by said first mentioned means for increasing or decreasing the supply of a medium whereby the value of said condition is maintained substantially constant, and the aforementioned means including a negative st motion adjustment mechanism operable automatically to effect an initial increase or decrease in the rate of supply of said medium which is relatively more rapid and larger than normal, upon each decrease or increase respectively in the value of said condition with respect to a value preselected therefor.

9. In a gas mixing control system, in combination, means including a calorimetric device continuously responsive to variations in the total heating value per unit volume of a flowing mixture of combustible gases, with respect to a value preselected therefor, means including a valve subject to control by said calorimetric device for varying the volumetric proportionality of said combustible gases whereby said value is maintained substantially constant, said valve having associated therewith a negative 10st motion adjustment mechanism whereby the former is initially subjected to a relatively rapid rate and relatively large degree of adjustment in one direction or the other upon each departure of said mixture from the total heating value per unit volume preselected therefor, and said last mentioned mechanism'also providing for subsequent intermittent adjustment of said valve in a like direction at a relatively slower rate pending departure of said mixture in an opposite sense from said total heating value per unit volume preselected therefor.

10. In a gas mixing control system, in combination, a pair of branch conduits through which a rich gas of variable total heating value per unit volume and a lean gas of constant total heating value per unit volume are respectively adapted to flow, an adjustable valve in one of said branch conduits, a main conduit into which said branch conduits discharge to provide for mixture of said gases, a calorimeter adapted to withdraw and burn a continuous volumetrically constant sample of said mixture to provide for ascertainment of the total heating value per unit volume thereof with respect to a value preselected therefor, a reversible electric motor subject to control by said calorimeter, and means comprising a negative lost motion driving connection between said motor and said valve, said negative lost motion driving connection servin to minimize the hunting period of adjustment of said valve as an incident to each increase or decrease in the total heating value per unit volume of said mixture resulting from an increase or decrease in the total heating value per unit volume of said rich gas.

11. In a control system, in combination, means responsive to variations in a condition such as temperature, means subject to control by said first mentioned means for increasing or decreasing the supply of a medium whereby the value of said condition is maintained substantially constant, the aforementioned means including means operable automatically to effect a relatively rapid and relatively large initial increase or decrease in the rate of supply of said medium upon each decrease or increase respectively in the value of said condition with respect to a value preselected therefor, said last mentioned means being also thereafter operable automatically to effect intermittent relatively smaller normal increases or decreases in said rate of supply pending attainment of a given value of said condition, for the purpose set forth.

12. In a control system of the character described, in combination, a conduit through which a combustible gas of variable total heating value per unit volume is adapted to flow, an adjustable valve in said conduit, means for continuously ascertaining the heating effect of combustion of said flow of gas, means responsive to variations in said heating effect for automatically adjusting said valve to vary the volumetric rate of flow of said gas whereby said heating effect is maintained substantially constant, said last mentioned means including a reversibl electric motor, gearing interposed between said motor and said valve to provide for opening or closing movement of the latter in accordance with the direction of operation of said motor, and means including a friction slip clutch associated with said gearing to compensate for inherent lost motion in the latter as an incident to each reversal of the direction of rotation of said motor, said last mentioned means being effective to provide for initial opening or closing movement of said valve at a rate faster than normal, for the purpose set forth.

13. In a control system of the character described, in combination, means responsive to variations in a condition such as temperature, means including an adjustable valve subject to control by said first mentioned means for increasing or decreasing the rate of supply of a medium whereby said condition is maintained at a predetermined substantially constant value, the aforementioned means including motor means operable automatically to effect a relatively rapid and relatively large initial adjustment of said valve to effect a corresponding relatively large initial increase or decrease in the rate of supply of said medium upon each decrease or increase respectively in the value of said condition with respect to the aforementioned value predetermined therefor, and the aforementioned means also acting to thereafter insure relatively slower and relatively smaller ad ustments of said valve, for the purpose set forth.

EDWIN X. SCHMIDT. 

